Advancement in robotics technology leads to an increase in need for applications thereof to medical devices. A vibration-type actuator such as that illustrated in FIG. 9 is used as a driving source of a high-precision manipulator. The vibration-type actuator is capable of providing direct driving without using a speed reduction mechanism. Furthermore, the vibration-type actuator has a holding torque that allows the manipulator to keep its attitude even in a state in which no electric power is supplied. The features described above make the vibration-type actuator suitable for use in a medical manipulator with high-precision position controllability.
PTL 1 discloses a vibration-type actuator suitable for use with a magnetic resonance imaging (MRI) apparatus. The vibration-type actuator is formed in a tube structure including an inner tube and an outer tube, and a stator and a rotor serving as a driving source of a puncture apparatus are formed such that the stator and the rotor extend in a longitudinal direction of the tube structure and such that the stator and the rotor are disposed respectively on the inner tube and the outer tube so as to oppose each other. To solve a problem with a vibration of the medical manipulator caused by a bending vibration that occurs in the tube structure of the actuator, a groove and a thread are formed so as to extend spirally around the inner tube and the outer tube and so as to fit with each other. One of the stator and the rotor of the vibration-type actuator are disposed on one of the groove and the thread, and the other one of the stator and the rotor is disposed on the other one of the groove and the thread.